The present invention relates to tags for use with electronic personnel monitoring systems and, more particularly, to tags for house arrest or related personnel monitoring systems whereby a person wearing the tag can be monitored for compliance with orders to remain at a prescribed location.
With the increasing overcrowding and expenses of jails and houses of detention, it has become increasingly popular in recent years to sentence an offender, particularly a non-violent offender, to house arrest. Thus, the offender is required to stay in a predesignated location, such as his residence, the residence of a responsible relative or a certain rehabilitating institution, for a certain duration. In some cases the offender is allowed, or even encouraged, to work or to conduct a business and his confinement to the predesignated location is limited to non-working hours.
While house arrest offers certain advantages over confinement in jails and similar institutions, the use of house arrest raises a problem of monitoring for compliance with the orders.
Various systems have been devised for monitoring for compliance of house arrest orders. The most popular systems involve the use of a tag which includes a miniature transmitter. The tag is strapped to the ankle or wrist of the offender. Running through the strap is an electrical circuit which is designed in such a way that the tag cannot be detached by an unauthorized party without breaking the circuit and alerting the authorities. The transmitter broadcasts an encoded signal, typically at regular intervals, over a pre-determined range, which roughly coincides with the area of confinement. A receiver-dialer located in the location of confinement, such as the offender's home, detects the signals form the transmitter and reports, typically over a telephone line, to a central monitoring facility so that any interruption in signal detection, such as would occur when the offender wanders beyond the transmitter range or when the tag is removed from the offender, is communicated to the monitoring facility.
The effectiveness of the tag is thus seen to be dependent on the ability to attach the tag to the offender in such a way that the tag cannot be removed without alerting the authorities. One approach to help make the tag tamper-proof has been to improve the mechanical attachment of the two ends of the strap. An example of this is disclosed in U.S. Pat. No. 4,812,823. A disadvantage of the locking system disclosed therein is that it is relatively complex.
Another approach has been to augment the electric circuit system with an additional system for detecting the removal of the tag from the offender. An example of such a system is disclosed in U.S. Pat. No. 4,885,571 which uses a pair of capacitive electrodes, one of which is realized with a conductive strap, which function as the plates of a capacitor with the body flesh serving as the dielectric material. When the tag is removed from the body of the offender, the system detects the change and alerts the authorities.
There is thus a widely recognized need for, and it would be highly advantageous to have, a tag for use with personnel monitoring systems which has enhanced tamper-resistant properties.